1. Field of the Invention
The present invention relates to semiconductor devices, and more particularly, to the use of thin films of nanowires in semiconductor devices.
2. Background Art
An interest exists in industry in developing low cost electronics, and in particular, in developing low cost, large area electronic devices. Availability of such large area electronic devices could revolutionize a variety of technology areas, ranging from civil to military applications. Example applications for such devices include driving circuitry for active matrix liquid crystal displays (LCDs) and other types of matrix displays, smart libraries, credit cards, radio-frequency identification tags for smart price and inventory tags, security screening/surveillance or highway traffic monitoring systems, large area sensor arrays, and the like.
The advancement of electronics has been moving towards two extremes in terms of physical scale. Rapid miniaturization of microelectronics according to Moore's law has led to increases in computing power while at the same time enabling reductions in cost. At the same time, progress has been made in the area of macroelectronics, in which electronic devices are integrated over large area substrates (e.g., having sizes measured in square meters). Current macroelectronics are primarily based on amorphous silicon (a-Si) or polycrystalline silicon (p-Si) thin film transistors (TFFs) on glass, and are finding important applications in various areas, including flat panel display (FPD), solar cells, image sensor arrays and digital x-ray imagers.
The current technology, however, is limited in what applications to which it can be applied. For example, there has been growing interest in the use of plastic as a substrate for macroelectronics due to various beneficial attributes of plastic, including flexibility, shock resistance, low weight, and low cost. However, the fabrication of high performance TFTs on plastics is difficult because process steps must be carried out below the glass transition temperature of the plastic. Significant efforts have been devoted to search for new materials (such as organics and organic-inorganic hybrids) or new fabrication strategies suitable for TFTs on plastics, but only with limited success. Organic TFTs have the potential for roll-to-roll fabrication process on plastic substrates, but with only a limited carrier mobility of about 1 cm2/V·s (centimeter squared per volt second). The limitations posed by materials and/or substrate process temperature (particularly on plastic) lead to low device performance, restricting devices to low-frequency applications. Therefore, applications that require even modest computation, control, or communication functions cannot be addressed by the existing TFT technology.
Individual semiconductor nanowires (NWs) and single walled carbon nanotubes can be used to fabricate nanoscale field effect transistors (FETs) with electronic performance comparable to and in some case exceeding that of the highest-quality single-crystal materials. In particular, carrier mobility of 300 cm2/V·s has been demonstrated for p-Si NWs, 2000-4000 cm2/V·s for n-indium InP NWs and up to 20,000 cm2/V·s for single walled carbon nanotubes. These nano-FETs are extending Moore's law toward the molecular level. They are, however, currently difficult to implement for production-scale nanoelectronics due to the complexity and limited scalability of the device fabrication processes.
Accordingly, what is needed are higher performance conductive or semiconductive materials and devices, and methods and systems for producing lower-cost, high performance electronic devices and components.
Furthermore, what is needed are high performance TFTs that can be applied to plastics and other substrates requiring low process temperatures.
What is also needed is a production scalable method for fabrication of nanoscale semiconductor devices than can be used as high performance TFTs.